1. Field of the Invention
This invention relates to a metal-work tool, particularly to a fastening device for a pneumatic punch assembly which can provide a punch operation or an edge-folding operation.
2. Description of the Prior Art
In a conventional pneumatic metal-work tool, the casing thereof has a position with a piston rod in the center thereof; one end of the piston rod extends into a hydraulic chamber, in which a push rod is furnished, and extends out; the end of the push rod is connected with a punch assembly. As soon as a pressure air is filled into the casing, the pressure air will push the piston to move, and simultaneously the piston rod in the hydraulic chamber will provide a pressure therein to cause a push rod to move and also to have the punch assembly to actuate for punch operation on a metal sheet. The hydraulic chamber on the front end of the casing is used for converting air power into a hydraulic power so as to obtain a higher punch force; however, a hydraulic leak could take place between the hydraulic chamber and the cylinder chamber after long time operation; in that case, the hydraulic push power would be reduced, and the oil in the hydraulic chamber must be replenished properly.
In a patent application Ser. No. 10/157,856, xe2x80x9cPneumatic Metal-work Toolxe2x80x9d of the applicant, a punch assembly is mounted on the front end of a hydraulic push-rod assembly; the hydraulic chamber of the hydraulic push-rod assembly is mounted with a piston rod, of which one end is mounted in a center hole of a piston in a cylinder. After a high pressure air is filled into the casing by means of a control-valve assembly, the pressure air will push the piston rod to move so as to have the pressure air converted into a hydraulic power by means of the hydraulic chamber, and then the hydraulic push rod will provide a punch force, and to cause the punch assembly to punch a hole or holes in a metal sheet; however, when a punch assembly having different size is changed, the punch distance has to be adjusted properly; therefore, it is deemed an inconvenient defect.
The prime object of the present invention is to provide a pneumatic metal-work tool, in which the punch assembly on the front end of the body can be replaced with different size without readjusting the punch distance by means of a threaded ring mounted on the threads of the body in the punch assembly.
Another object of the present invention is to provide a pneumatic metal-work tool, in which the threaded ring on the threads of the body of the punch assembly is furnished with threads on the inner curved surface thereof so as to facilitate the threaded ring to move along the threads of the cylindrical body of the punch assembly; the center curved surface of the threaded ring is furnished with a screw hole for receiving a stop screw; after the stop screw is set loose, the fastening ring around the threaded ring will be loosened; then, the threaded ring can be moved along the threads of the body of the punch assembly to adjust its position freely; finally, the threaded ring can be fastened to the body of the punch assembly with the stop screw so as to limit a given distance between the fastening ring and the threaded rod of the body of the pneumatic metal-work tool.
Still another object of the present invention is to provide a pneumatic metal-work tool, in which the threaded ring on the threads of the body of the punch assembly is mounted with a fastening ring; the inner curved surface of the fastening ring is furnished with threads and a cylindrical surface, which is used for receiving the threaded ring, and the inner side thereof has a shoulder portion to be in contact with the cylindrical surface of the threaded ring; the outer surface of the fastened ring is furnished with vertical threads and a through rectangular hole; the rectangular hole facilitates a hexagonal wrench to extend through so as to drive the stop screw on the threaded ring until the stop screw being fastened to the threads of the threaded rod and to limit the threaded ring to move; after the stop screw is set loose, the position of the threaded ring can be adjusted properly.
A further object of the present invention is to provide a pneumatic metal-work tool, in which the threaded ring and the fastening ring mounted on the threads of the cylindrical body of the punch assembly can be fastened to a different punch assembly directly for punch operation without adjusting the fastening distance upon changing a punch assembly having different size.